Telephony service providers of telephony (e.g., POTS and DSL) services utilize outside plants that provide connectivity from the subscribers of the service to the central offices (CO) of the service provider. The most common media used in the outside plant is copper loops. A copper loop typically transverses from the CO to the subscriber homes via manholes, wiring cabinets, pedestals, and poles before terminating at the network interface device (NID) at the subscribers' premises.
The manholes and cabinets represent major concentration sites for the wiring. Each cabinet or manhole (i.e., remote hub) typically serves about 500 homes. Each home is wired with approximately 3 to 5 pairs of coppers wires, depending on the practices of the service provider. Thus, about 1500 to 2500 subscriber-lines may terminate at such a remote hub. However, it is unlikely that all the subscriber lines are active. Accordingly, for cost and practical reasons, fewer amounts of wires (i.e., feeder lines) are laid between the remote hub and the central office.
A conventional remote hub includes two frames, one of which terminates a plurality of subscriber lines from the homes (subscriber premises), and the other frame terminates a plurality of feeder lines from a central office. Wiring connections between the two frames are made to provide end-to-end connectivity from the subscribers to the central office, and thereby provide conventional telephone services. In the current practice, such wire connections is performed manually by dispatching field personnel to the hub.
In addition to conventional telephone service, the service providers are currently implementing digital subscriber line (DSL) access as a means to provide broadband access (e.g., video and data) to the subscribers. In order to achieve a maximum rate, DSL service providers increasing deploy digital subscriber line access modems (DSLAMs) at the remote hubs, thereby decreasing the distance of the copper loop to the subscriber premises and increasing the speed of the DSL services. However, the broadband access market is very competitive with many service providers vying for the same market with a variety of the technologies (e.g., DSL, cable, fiber, etc.). This competitive market has resulted in a high subscriber chum (i.e., turnover) rate for such broadband services. Every “churn” of the DSL service typically entails the dispatch of a field technician to re-wire the connections at the remote hub. Dispatches are both costly and time consuming, and service provider would like to reduce these dispatches as much as possible. One method is to deploy an automatic cross-connect (AXC) system that switches analog signals at these hubs. Such AXCs can be controlled remotely by a technician at the network operations center.
In switching the analog signal, the connection through the cross-connect must be able to carry a fair amount of current (e.g., 250-300 milliamps). Further, the connectivity configuration must be maintained at the remote hub in the event of a power failure, thereby ensuring emergency service calls (e.g., 911 calls).
One prior art technique in building analog cross-connects that satisfy the above two requirements is to use electromechanical relay system, such as micro-electro-mechanical systems (MEMS). The current MEMS technology allows implementation of approximately fifty (50) double-posts single throw relays in an 80 pin chip. Each MEMS chip has a size of approximately ¾″×¾″, Such that a conventional 11″×18″ board of an automatic cross-connect switch (AXC) can accommodate approximately 150 of these chips, plus control and inter-connecting circuitry.
Even with the MEMS technology, cost and space is still major a consideration in the deployment of AXCs at remote hubs. Service providers still face the problem of whether to deploy a larger system, which provides more coverage but at higher costs, or a smaller systems that would be less costly but provide less coverage. Given these considerations, it is highly desirable to reduce the number of cross-points, and hence the number of MEMS cross-connect chips of the AXC, which would reduce both the cost and space requirement of the AXC switch.